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authorMichael Kerrisk <mtk.manpages@googlemail.com>2008-06-09 21:16:08 -0700
committerAl Viro <viro@zeniv.linux.org.uk>2008-06-23 08:43:04 -0400
commit4cca92264e61a90b43fc4e076cd25b7f4e16dc61 (patch)
treef7472b3dc27101761b92bb05ffff7785a73317f3 /fs/utimes.c
parent94c70b9ba7e9c1036284e779e2fef5be89021533 (diff)
downloadlwn-4cca92264e61a90b43fc4e076cd25b7f4e16dc61.tar.gz
lwn-4cca92264e61a90b43fc4e076cd25b7f4e16dc61.zip
[patch for 2.6.26 3/4] vfs: utimensat(): fix error checking for {UTIME_NOW,UTIME_OMIT} case
The POSIX.1 draft spec for utimensat() says: Only a process with the effective user ID equal to the user ID of the file or with appropriate privileges may use futimens() or utimensat() with a non-null times argument that does not have both tv_nsec fields set to UTIME_NOW and does not have both tv_nsec fields set to UTIME_OMIT. If this condition is violated, then the error EPERM should result. However, the current implementation does not generate EPERM if one tv_nsec field is UTIME_NOW while the other is UTIME_OMIT. It should give this error for that case. This patch: a) Repairs that problem. b) Removes the now unneeded nsec_special() helper function. c) Adds some comments to explain the checks that are being performed. Thanks to Miklos, who provided comments on the previous iteration of this patch. As a result, this version is a little simpler and and its logic is better structured. Miklos suggested an alternative idea, migrating the is_owner_or_cap() checks into fs/attr.c:inode_change_ok() via the use of an ATTR_OWNER_CHECK flag. Maybe we could do that later, but for now I've gone with this version, which is IMO simpler, and can be more easily read as being correct. Acked-by: Miklos Szeredi <miklos@szeredi.hu> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Ulrich Drepper <drepper@redhat.com> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/utimes.c')
-rw-r--r--fs/utimes.c36
1 files changed, 21 insertions, 15 deletions
diff --git a/fs/utimes.c b/fs/utimes.c
index d466bc587e6e..118d1c3241be 100644
--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -40,14 +40,9 @@ asmlinkage long sys_utime(char __user *filename, struct utimbuf __user *times)
#endif
-static bool nsec_special(long nsec)
-{
- return nsec == UTIME_OMIT || nsec == UTIME_NOW;
-}
-
static bool nsec_valid(long nsec)
{
- if (nsec_special(nsec))
+ if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
return true;
return nsec >= 0 && nsec <= 999999999;
@@ -106,7 +101,7 @@ long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags
times[1].tv_nsec == UTIME_NOW)
times = NULL;
- /* Don't worry, the checks are done in inode_change_ok() */
+ /* In most cases, the checks are done in inode_change_ok() */
newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
if (times) {
error = -EPERM;
@@ -128,15 +123,26 @@ long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags
newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
newattrs.ia_valid |= ATTR_MTIME_SET;
}
- }
- /*
- * If times is NULL or both times are either UTIME_OMIT or
- * UTIME_NOW, then need to check permissions, because
- * inode_change_ok() won't do it.
- */
- if (!times || (nsec_special(times[0].tv_nsec) &&
- nsec_special(times[1].tv_nsec))) {
+ /*
+ * For the UTIME_OMIT/UTIME_NOW and UTIME_NOW/UTIME_OMIT
+ * cases, we need to make an extra check that is not done by
+ * inode_change_ok().
+ */
+ if (((times[0].tv_nsec == UTIME_NOW &&
+ times[1].tv_nsec == UTIME_OMIT)
+ ||
+ (times[0].tv_nsec == UTIME_OMIT &&
+ times[1].tv_nsec == UTIME_NOW))
+ && !is_owner_or_cap(inode))
+ goto mnt_drop_write_and_out;
+ } else {
+
+ /*
+ * If times is NULL (or both times are UTIME_NOW),
+ * then we need to check permissions, because
+ * inode_change_ok() won't do it.
+ */
error = -EACCES;
if (IS_IMMUTABLE(inode))
goto mnt_drop_write_and_out;